Most earth drilling systems employ some form of rotary or percussion powered drills. Typically, a drilling machine, such as for forming a hole for an explosive charge, or for anchoring a roof bolt, includes a drill socket for receiving a stem with a drill bit on the distal down hole section thereof. The stem/bit on a rotary drill machine is rotated by a shaft, sometimes called a spinner, mounted on a drill head to form the drill hole. The rotary driving motion of the spinner is usually hydraulically or pneumatically driven.
To increase the efficiency of drilling, cuttings and dust are often collected and removed from adjacent the drill bit. The removal of the cuttings and dust from adjacent the drill bit reduces airborne contamination, provides clean cutting edges at the bottom of the hole, and allows the most efficient contact with the rock, or other strata. Typically, a pneumatic or hydraulic cuttings/dust collection/suppression and removal system is employed. In one example, pressurized air, or a suitable hydraulic fluid such as water, or an air/water mixture, is forced into the borehole to bail or pick up the cuttings and dust for disposal. In one particular embodiment, this goal is achieved by applying a vacuum on a center passage of the drill steel to draw bailing fluid into the borehole around the periphery of the drill steel, whereupon the cuttings and the dust particles are entrained and removed through the center passage. In either system, this withdrawn debris is initially pneumatically or hydraulically conveyed away from the drill hole. A typical drilling arrangement and cuttings/dust collecting system is shown in the prior art; Howeth, U.S. Pat. No. 4,434,861, and Wilson, U.S. Pat. Nos. 6,637,522 and 6,216,800, the disclosures of which are incorporated herein by reference.
When using air, the cuttings and dust are then filtered out at a remote location and disposed of. In systems where water is used, either exclusively or in a mixture with other fluids, an option is to simply allow the dust to be suppressed and then deposited outside the drill hole.
Regardless of which system is employed, debris may accumulate in the center passage and areas surrounding the center passage, during the removal of the cuttings and dust. The debris tends to form a cake-like substance, especially when it is wet and especially when the flow path is not completely linear. This accumulation of debris inhibits flow and prevents the effective conveyance of the cuttings and dust away from the borehole. When this occurs, the drill bit becomes isolated from the distal cutting face of the hole by the debris, and effective drilling cannot continue. In addition, the cuttings and dust begin to create airborne contamination. Thus, drilling is often interrupted to remove the debris, resulting in drilling delays, inefficiencies, and expenses.
Accordingly, a need is identified for a manner in which to assist in preventing the accumulation of debris in a flow path during a drilling operation, such as when forming a borehole in a face of a mine passage in association with a roof bolting operation.